Touch screens are electronic display input devices used by various systems to receive input from a user by touching the screen with a finger and stylus. The systems that use touch screens include computer systems, tablets, and mobile phones. Touch screens have also been referred to as touchpads or touch sensor devices.
Capacitive touch surfaces are one type of touch screen technology. Capacitive touch surfaces determine the position of an object, such as a finger or stylus, by detecting a change in capacitance due to a distortion in an electrostatic field that occurs when the touch screen is touched. Often capacitive touch surfaces have a set of transmitters and a set of receivers to determine the position of the location of where the touch screen was touched. The controller for the touch surface excites all the transmitters one after another to detect signals corresponding to objects in contact with the surface.
A passive pen is a convenient and cost efficient stylus used with touch screens. However, the signals generated from use of the passive pen on the touch screen are usually low magnitude and easily disturbed by noise. As a result, passive pen strokes that are produced by the touch screen are often discontinuous or jittery, which causes an unpleasant user experience.